The present invention relates to an anti-siphoning device for use in plumbing systems, and more particularly to an improved vacuum breaker.
The use and theory of vacuum breakers in plumbing systems is well known in the art. Essentially, the vacuum breaker allows an outlet or downstream side of the device to be vented to atmosphere to allow proper drainage thereof while preventing contamination of the upstream or inlet side due to siphoning of downstream liquid. Conventional vacuum breakers utilize a movable piston-like member movably disposed within a flow chamber of the device. As commonly understood, inlet flow pressure causes the piston to move upwards within the flow chamber thereby allowing the liquid to flow to the outlet side of the device. The outlet side is vented to allow proper drainage downstream of the outlet. At relatively high inlet pressures, the piston-like member essentially seals the outlet side of the device from the vent to prevent liquid passing directly from the inlet to the vent. With no inlet flow, the piston-like member seals the inlet side from the outlet while the outlet remains vented.
However, a substantial problem with conventional vacuum breakers is that during a condition of relatively low system inlet pressure, for example approximately 8 PSI and below, conventional vacuum breakers will leak due to "pumping" action of the piston within the flow chamber. During this low pressure flow, the water pressure forces the piston to rise within the flow chamber thereby allowing water to discharge through the outlet. However, the inlet flow pressure is not sufficient enough to move the piston within the chamber so as to seal the outlet from the vent. As the outlet volume of fluid increases due to, for example, restrictions in the outlet port or downstream backup, liquid tends to accumulate or flow back on top of the piston within the flow chamber. Subsequently, this water above the piston within is pumped out through the vent opening upon subsequent movement of the piston within the flow chamber. This leaking phenomena of conventional vacuum breakers is widely recognized in the industry as an unsatisfactory condition. With the present invention, applicant has substantially eliminated the leakage of vacuum breakers at relatively low system pressure flow.